Fluxgate sensor integrated in semiconductor substrate and method for manufacturing the same
A fluxgate sensor is integrated in a semiconductor substrate. The fluxgate sensor has two bar type soft magnetic cores, or a rectangular-ring type soft magnetic core to form a closed magnetic path on the semiconductor substrate, with an excitation coil formed of a metal layer either of the united structure winding the two bar-type cores or two longer sides of the rectangular-ring type core altogether and substantially in a number ‘8’ pattern, or of a separated structure winding the two bar type cores or two longer sides of the rectangular-ring type core, respectively, in a number ‘8’ pattern. Also, a pick-up coil is formed on the two bar-type cores or two longer sides of the rectangular-ring type core, either of the united structure winding the two bar-type cores or two longer sides of the rectangular-type core altogether in a solenoid pattern, or of the separated structure winding the two bar type cores or two longer sides of the rectangular-ring type core, respectively, in a solenoid pattern.
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1. Field of the Invention
The present invention generally relates to a fluxgate sensor, and more particularly, to a fluxgate sensor integrated in a semiconductor substrate and a manufacturing method thereof. The present application is based on Korean Patent Application No. 2002-13945, filed Mar. 14, 2002, which is incorporated herein by reference.
2. Description of the Prior Art
Existence of magnetic energy has been proven through various physical phenomena, and a fluxgate sensor enables a human to indirectly perceive magnetic energy, as it is unperceivable to human sense organs such as eyes and ears. As for the fluxgate sensor, a magnetic sensor employing a soft magnetic coil has been used for a long time. The magnetic sensor is made by winding a coil around a relatively large bar-shaped core or an annular core formed of a soft magnetic ribbon. Also, an electronic circuit is employed to obtain a magnetic field in proportion to the measured magnetic field.
The conventional fluxgate sensor, however, has the following problems. That is, due to the structure of the conventional fluxgate sensor in which the coil is wound around a large bar-shaped core or an annular core made of soft magnetic ribbon, production costs are high, and the volume of the overall system is large.
Also, flux leakage is inevitable in the flux change due to the excitation coil and the detected magnetic field. Accordingly, high sensitivity cannot be guaranteed.
SUMMARY OF THE INVENTIONThe present invention has been made to overcome the above-mentioned problems of the prior art. Accordingly, it is an object of the present invention to provide a high sensitivity fluxgate sensor integrated in a semiconductor substrate capable of not only reducing overall volume of a system, but also detecting a magnetic field with more accuracy, and a manufacturing method for manufacturing such a highly sensitive fluxgate sensor.
Another object of the present invention is to prevent an induction wave in a flux change detecting coil when the external magnetic field is measured as zero (0).
The above objects are accomplished by a fluxgate sensor according to the present invention, including: a soft magnetic core formed to form a closed magnetic path on a semiconductor substrate; an excitation coil formed as a metal film, winding the soft magnetic core; and a pick-up coil formed on the same plane as the excitation coil, the pick-up coil formed as a metal film for winding the soft magnetic core.
The soft magnetic core has two bars placed on the same plane in parallel relation. The two bars are positioned such that the length thereof lies in the direction of magnetic field detection. Meanwhile, the soft magnetic core can be formed as a rectangular-ring, and in this case also, the rectangular-ring is positioned to have its length in the direction of the magnetic field detection.
The excitation coil has a structure of alternately winding the two bars substantially in a number ‘8’ pattern. Alternatively, the excitation coil can have a structure of winding the two bars, respectively, and substantially in a solenoid pattern. When rectangular-ring is used for the soft magnetic core, the excitation coil either has a structure of alternately winding two longer sides of the rectangular-ring in the direction of magnetic field detection substantially in a letter ‘8’ pattern, or has a structure of winding the two longer sides, respectively.
The pick-up coil is placed on the same plane as the excitation coil that has a structure of alternately winding the two bars or two longer sides altogether in number ‘8’ pattern, or winding the two bars or two longer sides, respectively, in a solenoid pattern. The pick-up coil has a structure of winding the two bars or the two longer sides altogether, substantially in a solenoid pattern. Alternately, the pick-up coil can be placed on the same plane as the excitation coil that has a structure of winding the two bars or the two longer sides of the rectangular-ring altogether in the number ‘8’ pattern, or winding the two bars or the two longer sides of the rectangular-ring, respectively, in the solenoid pattern. In this case, the pick-up coil has a structure of winding the two bars or the two longer sides of the rectangular ring, respectively, in the solenoid pattern.
The above objects are also accomplished by a method for manufacturing a fluxgate sensor according to the present invention, including the steps of: forming a lower portion of an excitation coil and a pick-up coil by etching an upper surface of a semiconductor substrate according to a predetermined pattern for the lower portion for the excitation coil and the pick-up coil, and then firstly putting a metal in the etched area; forming a first insulating layer on the upper portion of the semiconductor substrate in which the metal is firstly put; forming first via holes by piercing through the insulating layer at locations distanced from each other by a predetermined distance, to interconnect with the metal firstly-put in the etched area; forming a soft magnetic core by bonding a soft magnetic film on an upper portion of the first insulating layer that has the first via holes formed therein, and patterning and etching; forming a second insulating layer on an upper portion of the semiconductor substrate that has the soft magnetic core formed therein; forming via holes interconnecting with the metal at locations corresponding to the first via holes; and forming an upper portion for the excitation coil and the pick-up coil by, applying a photosensitive material on an upper portion of the second insulating layer that has the second via holes formed therein; performing an etching according to the pattern for the upper portion of the excitation coil and the pick-up coil; and secondly putting a metal in the etched area.
The step of forming the lower portion for the excitation coil and the pick-up coil includes the steps of: applying a photosensitive material on the upper portion of the semiconductor substrate; forming a pattern for the lower portion of the excitation coil and the pick-up coil by an exposure with respect to the photosensitive material applied to the upper portion of the semiconductor substrate; etching according to the pattern for the lower portion of the excitation coil and the pick-up coil; forming an oxide layer on the upper portion of the semiconductor substrate on the etched section; forming a seed layer along the oxide layer; forming a metal layer on the upper portion of the semiconductor substrate, filling the etched area of the seed layer with the metal; and polishing the upper surface of the semiconductor substrate to insulate the metal of the etched area.
The step of forming the lower portion for the excitation coil and the pick-up coil includes the steps of: forming an oxide layer on the upper surface of the semiconductor substrate; forming a seed layer on an upper portion of the oxide layer; applying a thick photo resist on an upper portion of the seed layer; forming a pattern for the lower portion for the excitation coil and the pick-up coil by using an exposure with respect to the thick photo resist applied on the upper portion of the seed layer; forming a metal layer on the upper portion of the semiconductor substrate, filling the patterned area with a metal; and removing the seed layer and the photosensitive material that is applied on the upper portion of the seed layer to insulate the metal that is filled in the etched area for forming the lower portion for the excitation coil and the pickup coil.
The step of forming the upper portion for the excitation coil and the pick-up coil includes the steps of: applying the photosensitive material on the upper portion of the second insulating layer that has the second via holes formed therein; forming a pattern for the upper portion of the excitation coil and the pick-up coil by using an exposure with respect to the photosensitive material applied on the upper portion of the second insulating layer; forming a seed layer along the patterned section; secondly putting a metal in the patterned area corresponding to the pattern for the upper portion for the excitation coil and the pick-up coil; polishing the upper surface to insulate the metal filled in the patterned area; and removing the photosensitive material on the upper portion of the second insulating layer except the secondly-put metal.
The step of forming the upper portion for the excitation coil and the pick-up coil includes the steps of: forming a seed layer on an upper portion of the second insulating layer that has the second via holes formed therein; applying a thick photo resist on the upper portion of the seed layer; forming a pattern for an upper portion of the excitation coil and the pick-up coil by an exposure with respect to the thick photo resist applied on the upper portion of the seed layer; putting a metal in the patterned area corresponding to the upper portion of the excitation coil and the pick-up coil; and removing the seed layer and the thick photo resist that is applied on the upper portion of the seed layer, to insulate the metal that is filled in the patterned area for forming the upper portion of the excitation coil and the pick-up coil.
According to the present invention, by forming a soft magnetic core along a direction of magnetic field detection, counter-magnetic properties can be reduced, while there is no induction wave in a flux change detecting coil due to the structure in which a magnetic field change detecting coil is mounted on an excitation coil that is wound around the soft magnetic core.
The above-mentioned objects and the feature of the present invention will be more apparent by describing the preferred embodiment of the present invention by referring to the appended drawings, in which:
From now on, the present invention will be described in greater detail by referring to the appended drawings.
In the fluxgate sensor, first and second bar-type soft magnetic cores 1 and 2 in parallel with each other are wound by an excitation coil 3 substantially in a number ‘8’ pattern, and a pick-up coil 4 is formed on the excitation coil 3, winding the first and the second soft magnetic cores 1 and 2 altogether. The excitation coil 3 can be wound around the first and second bar-type soft magnetic cores 1 and 2, respectively. Also, the pick-up coil 4 can have the structure formed on the excitation coil 3, winding the first and second bar-type soft magnetic cores 1 and 2, respectively.
For convenience in explanation, let us call the structure winding the first and second soft magnetic cores in a number ‘8’ pattern a ‘united structure’, and the structure winding the first and second soft magnetic cores respectively a ‘separated structure’. In the case of a rectangular-ring type soft magnetic core, which will be described later in the second preferred embodiment, the structure winding two longer sides of the rectangular-ring type soft magnetic core in a number ‘8’ pattern will be called a ‘united structure’, while the structure winding the two longer sides, respectively, will be called a ‘separated structure’.
With the excitation coil 3 wound around the first and second bar-type soft magnetic cores 1 and 2 in the number ‘8’ pattern as shown in
The pick-up coil 4 is wound to obtain the sum of the flux in each of the cores 1 and 2, and to detect the flux changes by the electronic induction caused by the AC excitation current. Since the induction voltage at the pickup coil 4 has internal magnetic fields acting in opposite directions, the induction voltage detected at the pick-up coil 4 is the result of offsetting the two symmetrically generated induction voltages Vind1 and Vind2 (
In the fluxgate sensor constructed as described above, it is most important to have the appropriate structure of two soft magnetic cores 1 and 2, the excitation coil 3 of the united structure winding the two soft magnetic cores 1 and 2 in a number ‘8’ pattern, and the pick-up coil 4 winding over the excitation coil 3 in the solenoid pattern. This is because, in the absence of the external magnetic field Hext, such structure offsets the induction waves of the magnetic fields generated by the first and second bar-type soft magnetic cores 1 and 2, and the flux generated by the excitation coil 3 forms a closed magnetic path.
The soft magnetic core of
The detection of a magnetic field is also possible by the structure of a single bar-type core being arranged with the excitation coil and the pick-up coil. This case, however, requires more complicated signal processing of the output from the detecting coil such as amplification and filtering, because there are induction voltage waves generated at the detection coil by the larger excitation coil even in the absence of the external magnetic field. Accordingly, using either the two bar-type cores or a single rectangular-ring type core will allow more advantages, especially in terms of signal processing requirements.
The process of producing the fluxgate sensor will be described below.
First, by using a photosensitive material and an exposure on an upper side of a semiconductor substrate 21, a pattern is formed for an excitation coil and a pick-up coil, according to which the excitation coil and the pick-up coil alternately wind one time, respectively. Then, through an etching, a high-section-rate surface 22 is formed according to the pattern. Next, an oxide film (not shown) is formed over the etched section of the semiconductor substrate 21 for electric insulation (
Meanwhile, as shown in
On the upper portion of the substrate 21, which has the lower portion for the excitation coil and the pick-up coil, a first insulating layer 24 is formed (
Next, on the upper portion of the second insulating layer 26 having the second via holes 27 formed therethrough, a photosensitive material is applied, and patterned through the exposure corresponding to the upper portion of the excitation coil and the pick-up coil. Also according to a predetermined pattern, a shape of the upper portion (not shown) of the excitation coil and the pick-up coil is formed. Then, along the section of the patterned area, a seed layer (not shown) is formed. A second metal layer (not shown) is then formed, by secondly filling the etched area with metal 28. After that, in order for the metal 28 in the etched area to be insulated, the chemical mechanical polishing (CMP) is performed. By removing the photosensitive material applied onto the upper portion of the second insulating layer excluding the secondly-put metal 28, the upper portion of the excitation coil and the pick-up coil is formed (
Meanwhile, in addition to the process of forming the upper portion of the excitation coil and the pick-up coil as described above with reference to
First, after forming the seed layer on the upper portion of the second insulating layer 26 which has the second via hole 27 formed therein, the thick photo resist is applied onto the upper portion of the seed layer. By using the exposure with respect to the thick photo resist applied onto the upper portion of the seed layer, the pattern for the upper portion of the excitation coil and the pick-up coil is formed, and continuously, etching is performed according to such pattern. Next, the upper portion of the excitation coil and the pick-up coil is formed by putting the metal 28 into the etched area corresponding to the upper portion of the excitation coil and the pick-up coil, and then by removing the seed layer and the thick photo resist applied to the upper portion of the seed layer in a manner of insulating the metal 28 of the etched area.
The induction voltage detected at the pick-up coil according to the second preferred embodiment is similar to the induction voltage detected in the excitation coil of the united structure according to the first preferred embodiment of the present invention. Also, the fluxgate sensor according to the second embodiment functions to offset the induction voltage in the absence of an external magnetic field, which is also similar to the first embodiment.
The fluxgate sensor described above can be used in various applications, such as, but not by way of limitation, a navigation system by terrestrial magnetism detection, an earth magnetism change monitor (earthquake prediction), a biological electric measurement device, and an apparatus for detecting defects in metals. As for indirect applications, the fluxgate sensor can also be used, for example, but not by way of limitation, in a magnetic encoder, a contactless potentiometer, an electric current sensor, a torque sensor, and a displacement sensor.
As the fluxgate sensor integrated in the semiconductor substrate according to the present invention can be integrated with other sensors and circuits, the overall size of the system can be greatly reduced, and low power consumption is achieved.
Also, the system can be compact-sized, and the sensitivity is kept high to detect even a weak external magnetic field as it variably drives the voltages induced from the respective cores of sides.
Also, as the fluxgate sensor according to the present invention can be produced at a cheaper price than the bar-type cores or annular cores, mass-production is enabled.
Although preferred embodiments of the present invention have been described, it will be understood by those skilled in the art that the present invention should not be limited to the described preferred embodiments, but various changes and modifications can be made within the spirit and scope of the present invention as defined by the appended claims.
Claims
1. A fluxgate sensor, comprising:
- a soft magnetic core which forms a closed magnetic path on a semiconductor substrate;
- an excitation coil formed as a first metal film, winding the soft magnetic core; and
- a pick-up coil formed as a second metal film for winding the soft magnetic core, wherein the soft magnetic core comprises two bars, the two bars disposed co-planar on a plane that runs substantially parallel with the substrate;
- wherein a longitudinal axis of the soft magnetic core is substantially parallel to the semiconductor substrate,
- wherein the semiconductor substrate includes a trench structure, and
- wherein a lower portion of the excitation coil and the pick up coil is embedded in the trench structure.
2. The fluxgate sensor of claim 1, wherein the two bars have their length in a direction of magnetic field detection.
3. The fluxgate sensor of claim 2, wherein the excitation coil has a structure of alternately winding the two bars substantially in a number ‘8’ pattern.
4. The fluxgate sensor of claim 3, wherein the pick-up coil has a structure formed of winding the two bars altogether substantially in a solenoid pattern.
5. The fluxgate sensor of claim 3, wherein the pick-up coil has a structure formed of winding the two bars, respectively, and substantially in a solenoid pattern.
6. The fluxgate sensor of claim 2, wherein the excitation coil has a structure of winding the two bars, respectively, and substantially in a solenoid pattern.
7. The fluxgate sensor of claim 6, wherein the pick-up coil has a structure formed on a plane same as the excitation coil, winding the two bars altogether substantially in a solenoid pattern.
8. The fluxgate sensor of claim 6, wherein the pick-up coil has a structure formed of winding the two bars, respectively, and substantially in a solenoid pattern.
9. The fluxgate sensor of claim 1, wherein the soft magnetic core comprises a rectangular-ring.
10. The fluxgate sensor of claim 9, wherein the rectangular ring has its length in the direction of magnetic field detection.
11. The fluxgate sensor of claim 10, wherein the excitation coil has a structure of alternately winding two longer sides of the rectangular ring, substantially in a number ‘8’ pattern.
12. The fluxgate sensor of claim 11, wherein the pick-up coil has a structure of winding the two longer sides of the rectangular ring altogether substantially in a solenoid pattern.
13. The fluxgate sensor of claim 11, wherein the pick-up coil has a structure of winding the two longer sides of the rectangular ring, respectively, and substantially in a solenoid pattern.
14. The fluxgate sensor of claim 10, wherein the excitation coil has a structure of winding the two longer sides of the rectangular ring, respectively, and substantially in a solenoid pattern.
15. The fluxgate sensor of claim 14, wherein the pick-up coil has a structure of winding the two longer sides of the rectangular ring altogether substantially in a solenoid pattern.
16. The fluxgate sensor of claim 14, wherein the pick-up coil has a structure of winding the two longer sides of the rectangular ring, respectively, and substantially in a solenoid pattern.
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Type: Grant
Filed: Sep 12, 2002
Date of Patent: Jul 7, 2009
Patent Publication Number: 20030173963
Assignee: Samsung Electronics Co., Ltd. (Suwon-si)
Inventors: Won-youl Choi (Suwon), Kyung-won Na (Yongin), Sang-on Choi (Suwon)
Primary Examiner: Reena Aurora
Attorney: Sughrue Mion, PLLC
Application Number: 10/241,558
International Classification: G01R 33/04 (20060101); G01R 33/02 (20060101);